Area Forecast Discussion
Issued by NWS Little Rock, AR

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510
FXUS64 KLZK 071750 AAC
AFDLZK

Area Forecast Discussion...UPDATED
National Weather Service Little Rock AR
1150 AM CST Wed Dec 7 2016

.UPDATE...

Updated for the 18z aviation discussion below.

&&

.AVIATION...

Regional radar imagery shows precipitation is light and having a
hard time reaching the ground. This along with lighter precip
forecasts from the models leads me to believe that prevailing
precip (be it frozen or liquid) will not be an issue in the TAFs.
That said, there have been some reports of flurries in NE OK this
morning, and the western part of the state is the most likely
area for any precip to hit the ground through the 18z TAF period.
As such, left -SN in a TEMPO at KHRO from 20z- 00z, and a PROB30
group for -SN at KHOT and KADF after midnight tonight. That should
cover things nicely. Otherwise, MVFR cigs are the only flight
concern to speak of. Those are pervasive across all but northern
Arkansas this morning. Expect those to stick around through late
tonight before the arctic front pushes through Arkansas and clears
things out.

&&

.PREV DISCUSSION...(ISSUED 856 AM CST Wed Dec 7 2016)

UPDATE...

Issuing a mid-morning update here to freshen up the forecast and
account for the latest trends. Regional radar observations show
fairly expansive area of very light precip noted across Kansas and
into western Missouri and northeastern Oklahoma this morning. This
is beneath the developing +100kt jet streak over that same region.
Chats with surrounding offices reveal that some light snow
flurries are making it to the ground at the Tulsa office. Also
have had some reports of drizzle in central, western, and
southwestern parts of Arkansas which is consistent with guidance.
As the arctic front arrives today, expect the bulk of that light
precip to our northwest, to propagate southward. The latest high
resolution CAM models show the precip mainly holding to western
Arkansas, which makes sense given the weak cold air damming setup
we have across the eastern part of the state thanks to surface
high pressure anchored over southern IL/IN. As such, have trended
the PoP forecast to account for, generally speaking, higher
precip chances remaining over the western half of the forecast
area today.

Getting back to precip types, with such low surface dewpoints and
wet bulb zero heights, snow or a rain/snow mix will likely be
possible throughout the day in the northwest. Again, precip rates
and amounts will be low so no notable accumulations or impacts are
expected. Grassy areas may see a couple of tenths of accumulations
but that should be about the gist of it I think. Further south, a
rain/snow mix will gradually transition southward with the precip
as temperatures fall into the mid 30s. Generally, used the 35 F
line as the transition to rain/snow since dewpoints should be
below freezing by the time any given spot drops to that
temperature later this afternoon and evening.


Prev Discussion.../ Issued 308 AM CST Wed Dec 7 2016/

Main concerns in this forecast cycle are chances of precipitation
today and tonight, with some potential for a wintry mix. Although
amounts will be very light. Temperature forecast will also be a
challenge with cooler to much colder than normal temperatures
today through Saturday, while a slow warm up over the weekend
into next week.

Surface high pressure was over the region, but low to mid level
moisture has developed clouds over AR to create cloud to mostly
cloudy conditions. A few areas of patchy drizzle was also noted
over southern to central AR. Temperatures were from the upper 20s
to mid 30s in northern AR, while 40s in central and southern AR.
Surface winds were light from the north to northeast. Aloft the
broad upper low pressure system was over the central part of the
U.S. with some moisture and weak shortwave energy within the west
flow.

SHORT TERM...Today Through Thursday Night

Today clouds will hold over much of AR, while temperatures will
remain in the 40s north to central, while to some lower 50s in
the south. Weak shortwave energy may develop patchy light rain or
just some drizzle or sprinkles this morning mainly over
southwestern AR. This afternoon, some patchy light rain/drizzle or
sprinkle may again be seen over western to central AR, as more
weak shortwave energy moves into AR within the upper west flow.
Rain amounts will be very light. Later this evening and especially
overnight, temperatures will lower below freezing behind the
expected cold front ushering in much colder air. Moisture amounts
are quite limited, but some light rain mixing with light snow or
flurries or light snow may develop on the back side of the front
as it moves southeast, and as the moisture rings out. Ground
temperatures remain well above freezing, and any light snow that
falls would be seen in grassy areas, elevated locations and in
normally colder locations. Some slick spots could develop on wet
roads before the precipitation ends. Then breezy and much colder
weather conditions for Thursday to Friday, with the coldest air of
the late Fall Season. Lows Thursday morning will be in the 20s to
30s, while Friday night in the teens to 20s. Highs will only reach
the 30s to 40s on Thursday.

LONG TERM...Friday Through Tuesday

By Friday, the airmass will start to modify a bit, as the center
of surface high pressure moves across the region, and winds begin
to take on more of a southerly component. By late Saturday, low
pressure developing in the plains will drag a frontal boundary
into the region. Rain will develop and spread into the region late
Saturday or early Sunday. At this point, thunder doesn`t look
likely, as there`s not really a tremendous amount of upper level
energy with the system.

Front will pass Sunday afternoon or night, with colder air following
into the region. There will be a possibility of some light wintry
precipitation as the system moves out on Sunday night, primarily in
the northwest, but this far out, impacts, if any at all, are
uncertain. High pressure will move through quickly behind this
system, with another front affecting the area just beyond the end of
the period, and more cold air spilling down into the central and
southern United States.

&&

.LZK Watches/Warnings/Advisories...NONE.
&&

$$


Aviation...64



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